sErik 
February 8, 2010 06:22 
BC settings to expand pressure on atmosphere  simpleFoam / totalPressure
Hi Foamers,
I have a problem with the definition of boundary conditions.
I'm running a relativly easy case  standard backward facing step  with simpleFoam (kepsilon turbulence model) to compare the OF results with some other calculations.
At the inlet I have a velocity of 6,02 m/s and at the outlet I want the pressure to expand to normal atmospheric pressure (101325 Pa). My problem is, that I don't realy know, how to set the correct conditions for the inlet/outlet.
At the moment I have for U
Quote:
inlet
{
type fixedValue;
value uniform (6.02 0 0);
}
outlet
{
type fixedValue;
value uniform (0 0 0);
}
wall
{
type fixedValue;
value uniform (0 0 0);
}

and for p
Quote:
inlet
{
type zeroGradient;
}
outlet
{type fixedValue;
value uniform 0;
}
wall
{
type zeroGradient;
}

My boundarys are
Quote:
inlet
{
type patch;
physicalType inlet;
}
outlet
{
type patch;
physicalType outlet;
}

With these settings, the simulation runs fine, but it's not exactly what I need.
I tried totalPressure with these settings  wall stays the same:
for p
Quote:
inlet
{
type totalPressure;
p0 uniform 1.01325e+05;
U U;
phi phi;
rho none;
psi none;
gamma 1.4;
}
outlet
{
type totalPressure;
p0 uniform 1.01325e+05;
U U;
phi phi;
rho none;
psi none;
gamma 1.4;
}

for U
Quote:
inlet
{
type fixedValue;
value uniform (6.02 0 0);
}
outlet
{
type zeroGradient;
}

But then the simulation crashes after a few steps:
Quote:
Time = 0.4
DILUPBiCG: Solving for Ux, Initial residual = 0.4226, Final residual = 0.0131669, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.385886, Final residual = 0.00659647, No Iterations 1
GAMG: Solving for p, Initial residual = 0.993287, Final residual = 0.00404666, No Iterations 1
time step continuity errors : sum local = 14029.9, global = 1.97454, cumulative = 52.1146
DILUPBiCG: Solving for epsilon, Initial residual = 0.245904, Final residual = 0.00112502, No Iterations 1
bounding epsilon, min: 5.08864e+15 max: 2.93019e+16 average: 6.86567e+11
DILUPBiCG: Solving for k, Initial residual = 0.796412, Final residual = 0.0271624, No Iterations 1
bounding k, min: 7.85411e+07 max: 3.01688e+10 average: 2.10361e+06
ExecutionTime = 5.7 s ClockTime = 6 s
Time = 0.5
DILUPBiCG: Solving for Ux, Initial residual = 0.00899943, Final residual = 3.74612e05, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.0728675, Final residual = 9.68172e05, No Iterations 1
GAMG: Solving for p, Initial residual = 0.976204, Final residual = 0.00756845, No Iterations 5
time step continuity errors : sum local = 211598, global = 3456.42, cumulative = 3404.3
DILUPBiCG: Solving for epsilon, Initial residual = 2.35526e05, Final residual = 3.37908e07, No Iterations 1
bounding epsilon, min: 1.98511e+19 max: 4.34557e+20 average: 1.11602e+16
DILUPBiCG: Solving for k, Initial residual = 0.000959334, Final residual = 1.61051e05, No Iterations 1
bounding k, min: 2.44986e+14 max: 9.10124e+14 average: 8.71869e+09
ExecutionTime = 6.37 s ClockTime = 7 s
Time = 0.6
DILUPBiCG: Solving for Ux, Initial residual = 0.587131, Final residual = 0.00365698, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.381925, Final residual = 0.0271016, No Iterations 1
GAMG: Solving for p, Initial residual = 1, Final residual = 0.0082871, No Iterations 7
time step continuity errors : sum local = 4.51584e+49, global = 1.07389e+49, cumulative = 1.07389e+49
DILUPBiCG: Solving for epsilon, Initial residual = 1, Final residual = 0.00710696, No Iterations 1
bounding epsilon, min: 7.62782e+71 max: 8.5466e+73 average: 1.90599e+69
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.00716964, No Iterations 1
bounding k, min: 6.71536e+58 max: 3.06377e+59 average: 1.93931e+55
ExecutionTime = 7.11 s ClockTime = 8 s
Time = 0.7
DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.00874036, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 0.00873079, No Iterations 1
#0 Foam::error::printStack(Foam::Ostream&) in "/opt/OpenFOAM/OpenFOAM1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#1 Foam::sigFpe::sigFpeHandler(int) in "/opt/OpenFOAM/OpenFOAM1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#2 ?? in "/lib/libc.so.6"
#3 Foam::PCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/OpenFOAM/OpenFOAM1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#4 Foam::GAMGSolver::solveCoarsestLevel(Foam::Field<d ouble>&, Foam::Field<double> const&) const in "/opt/OpenFOAM/OpenFOAM1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#5 Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMa trix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const in "/opt/OpenFOAM/OpenFOAM1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#6 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/opt/OpenFOAM/OpenFOAM1.6/lib/linux64GccDPOpt/libOpenFOAM.so"
#7 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/opt/OpenFOAM/OpenFOAM1.6/lib/linux64GccDPOpt/libfiniteVolume.so"
#8 main in "/opt/OpenFOAM/OpenFOAM1.6/applications/bin/linux64GccDPOpt/simpleFoam"
#9 __libc_start_main in "/lib/libc.so.6"
#10 _start at /usr/src/packages/BUILD/glibc2.9/csu/../sysdeps/x86_64/elf/start.S:116

It's clear, that bounding k and epsilon diverge, but I don't understand why. With the first settings, I get fine results.
How do I have to specify the correct BC for the velocity/pressure for my case?
I would realy appreciate your help!
Regards,
Erik
€dit
This is my kfile
Quote:
inlet
{
type fixedValue;
value uniform 0.0748;
}
outlet
{
type zeroGradient;
}
wall
{
type kqRWallFunction;
value uniform 0.0748;
}

This is epsilon
Quote:
inlet
{
type fixedValue;
value uniform 0.960;
}
outlet
{
type zeroGradient;
}
wall
{
type epsilonWallFunction;
value uniform 0.960;
}

